1. Field of the Invention
The present invention relates to a refractive index detector for detecting a refractive index difference between a sample cell through which a sample flows and a reference cell containing a reference liquid, based on the behavior of light which has passed through the sample cell and the reference cell, and for measuring the concentration of a sample flowing through the sample cell based on the refractive index difference, and a liquid chromatograph that uses the refractive index detector.
2. Description of the Related Art
A refractive index detector is used by a liquid chromatograph as a detector for detecting a sample component separated by an analytical column. The refractive index detector includes a sample cell and a reference cell that are provided being separated from each other by a partition wall, and causes a sample solution to flow in the sample cell in a state where a reference liquid (a solvent not containing the sample) is contained in the reference cell, and measures the behavior of light which has passed through the sample cell and the reference cell at this time. The optical path of the transmission light changes according to the refractive index difference between the sample cell and the reference cell. Accordingly, if the amount of displacement from a reference position of the slit image of the transmission light is detected, the concentration of the sample flowing through the sample cell may be determined.
Such a refractive index detector generally includes one inlet port and one outlet port for connecting pipes, and switches, by a switching valve, between whether a liquid supplied from the inlet port is to flow along the route of sample cell-reference cell-outlet port, or along the route of sample cell-outlet port (for example, see FIG. 3 of JP 2006-162262A). In the case of causing the liquid to flow along the route of sample cell-outlet port, the outlet of the reference cell is closed.
When supplying a reference liquid to the reference cell, a solvent not containing a sample is caused to flow, as a reference liquid, along the route of sample cell-reference cell-outlet port, and the reference cell is filled with the reference liquid. After the reference cell is filled with the reference liquid, the switching valve is switched so that the liquid flows along the route of the sample cell-outlet port, and the sample concentration in the sample solution flowing through the sample cell is detected based on the refractive index difference between the sample cell and the reference cell.